U.S. patent number 10,618,849 [Application Number 15/501,370] was granted by the patent office on 2020-04-14 for method for producing a hydrophobic heat-insulating molded body.
This patent grant is currently assigned to Evonik Operations GmbH. The grantee listed for this patent is Evonik Operations GmbH. Invention is credited to Uwe Albinus, Johannes Daenner, Manfred Dannehl, Gabriele Gaertner, Matthias Schindler.
United States Patent |
10,618,849 |
Albinus , et al. |
April 14, 2020 |
Method for producing a hydrophobic heat-insulating molded body
Abstract
Process for the production of a hydrophobic thermal-insulation
moulding, where a hydrophilic thermal-insulation moulding is
brought into contact with a hydrophobizing agent in vapour form
with formation of a thermal-insulation moulding coated with
hydrophobizing agent, and this is then subjected to a press process
and during the press process and/or after the press process is
reacted with the hydrophobizing agent with formation of the
hydrophobic thermal-insulation moulding, where a) the density of
the hydrophobic thermal-insulation moulding after the press process
and after the reaction with the hydrophobizing agent is from 100 to
250 kg/m.sup.3, and b) the density of the hydrophilic
thermal-insulation moulding on contact with the hydrophobizing
agent is from 50% to less than 100% of the density of the
hydrophobic thermal-insulation moulding.
Inventors: |
Albinus; Uwe (Bad Vilbel,
DE), Daenner; Johannes (Kaltensundheim,
DE), Dannehl; Manfred (Kahl am Main, DE),
Schindler; Matthias (Gelsenkirchen, DE), Gaertner;
Gabriele (Hanau, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Evonik Operations GmbH |
Essen |
N/A |
DE |
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Assignee: |
Evonik Operations GmbH (Essen,
DE)
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Family
ID: |
51292862 |
Appl.
No.: |
15/501,370 |
Filed: |
July 27, 2015 |
PCT
Filed: |
July 27, 2015 |
PCT No.: |
PCT/EP2015/067102 |
371(c)(1),(2),(4) Date: |
February 02, 2017 |
PCT
Pub. No.: |
WO2016/020215 |
PCT
Pub. Date: |
February 11, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170233297 A1 |
Aug 17, 2017 |
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Foreign Application Priority Data
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Aug 8, 2014 [EP] |
|
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14180309 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B
41/009 (20130101); B28B 3/123 (20130101); C04B
41/64 (20130101); C04B 30/02 (20130101); C04B
30/00 (20130101); C04B 35/64 (20130101); B28B
11/04 (20130101); C04B 32/00 (20130101); C04B
41/4944 (20130101); B28B 1/52 (20130101); F16L
59/028 (20130101); C04B 35/82 (20130101); C04B
30/00 (20130101); C04B 14/066 (20130101); C04B
14/324 (20130101); C04B 14/42 (20130101); C04B
24/42 (20130101); C04B 40/0071 (20130101); C04B
40/0259 (20130101); C04B 30/00 (20130101); C04B
14/066 (20130101); C04B 14/42 (20130101); C04B
24/42 (20130101); C04B 40/0071 (20130101); C04B
40/0259 (20130101); C04B 2103/56 (20130101); C04B
32/00 (20130101); C04B 14/066 (20130101); C04B
14/324 (20130101); C04B 14/42 (20130101); C04B
24/42 (20130101); C04B 40/0071 (20130101); C04B
40/0259 (20130101); C04B 30/02 (20130101); C04B
14/066 (20130101); C04B 14/324 (20130101); C04B
14/42 (20130101); C04B 24/42 (20130101); C04B
40/0071 (20130101); C04B 40/0259 (20130101); C04B
41/009 (20130101); C04B 14/324 (20130101); C04B
14/42 (20130101); C04B 41/4944 (20130101); C04B
41/0072 (20130101); C04B 41/4521 (20130101); C04B
41/4529 (20130101); C04B 2235/614 (20130101); C04B
2235/3418 (20130101); C04B 2235/9607 (20130101); C04B
2111/27 (20130101); C04B 2235/77 (20130101); C04B
2235/5216 (20130101); C04B 2235/3826 (20130101); C04B
2111/28 (20130101) |
Current International
Class: |
B28B
3/12 (20060101); C04B 30/02 (20060101); F16L
59/02 (20060101); C04B 35/64 (20060101); B28B
11/04 (20060101); C04B 32/00 (20060101); C04B
41/00 (20060101); C04B 41/64 (20060101); C04B
30/00 (20060101); C04B 41/49 (20060101); C04B
35/82 (20060101); B28B 1/52 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10 2007 042 000 |
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Mar 2009 |
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DE |
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10 2010 005 800 |
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Jul 2011 |
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DE |
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1 988 228 |
|
Nov 2008 |
|
EP |
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1 988 228 |
|
Nov 2008 |
|
EP |
|
WO 2013/013714 |
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Jan 2013 |
|
WO |
|
WO-2013013714 |
|
Jan 2013 |
|
WO |
|
Other References
International Search Report dated Oct. 14, 2015 in
PCT/EP2015/067102 filed Jul. 27, 2015. cited by applicant .
European Search Report dated Feb. 2, 2015, in European Patent
Application No. 14180309.8 filed Aug. 8, 2014. cited by
applicant.
|
Primary Examiner: Yuan; Dah-Wei D.
Assistant Examiner: Dagenais-Englehart; Kristen A
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
The invention claimed is:
1. A process for producing a hydrophobic thermal-insulation
molding, comprising: contacting a hydrophilic thermal-insulation
molding with a hydrophobizing agent in the form of vapor, thereby
forming a thermal-insulation molding coated with the hydrophobizing
agent; pressing the thermal-insulation molding coated with the
hydrophobizing agent; and during and/or after the pressing, heating
the thermal-insulation molding coated with the hydrophobizing
agent, thereby forming the hydrophobic thermal-insulation moulding
molding, wherein the hydrophilic thermal-insulation molding
comprises a thermal-insulation mixture comprising a fine-particle
silica, IR opacifier and fiber material, the contacting, the
pressing, and the heating take place between two gas-permeable
moving belts of a press, a density of the hydrophobic
thermal-insulation molding the heating is from 100 to 250
kg/m.sup.3, and a density of the hydrophilic thermal-insulation
molding contacted with the hydrophobizing agent is from 50% to less
than 100% of the density of the hydrophobic thermal-insulation
molding.
2. The process according to claim 1, wherein in the contacting, a
contact temperature T.sub.contact is from -30.degree. C. to
150.degree. C.
3. The process according to claim 1, wherein in the heating, a
reaction temperature T.sub.reaction is from 50.degree. C. to
500.degree. C.
4. The process according to claim 1, wherein a contact time during
the contacting and a heating time during the heating are in each
case from 1 minute to 1 hour.
5. The process according to claim 1, wherein the contacting and the
heating take place in a chamber, and wherein the hydrophobizing
agent is introduced into the chamber until a pressure difference
.DELTA.p is .gtoreq.20 mbar, wherein .DELTA.p=p.sub.2-p.sub.1, and
p.sub.1=pressure in the chamber before the introduction of the
hydrophobizing agent, and p.sub.2=pressure in the chamber at which
the introduction of the hydrophobizing agent is stopped.
6. The process according to claim 1, wherein the fine-particle
silica is a fumed silica.
7. The process according to claim 1, wherein a proportion of the
fine-particle silica, based on the thermal-insulation mixture, is
from 70 to 95% by weight.
8. The process according to claim 1, wherein a proportion of the IR
opacifier, based on the thermal-insulation mixture, is from 2 to
20% by weight.
9. The process according to claim 1, wherein a proportion of the
fiber material, based on the thermal-insulation mixture, is from 3
to 10% by weight.
10. The process according to claim 1, wherein the hydrophobizing
agent is at least one organosilicon compound selected from the
group consisting of R.sub.n--Si--X.sub.4-n and
R.sub.3Si--Y--SiR.sub.3, wherein n=from 1 to 3; R.dbd.--CH.sub.3 or
--C.sub.2H.sub.5; X.dbd.--Cl, --Br, --OCH.sub.3, --OC.sub.2H.sub.5,
or --OC.sub.3H.sub.8; and Y.dbd.NH or O.
11. The process according to claim 1, wherein a proportion of the
hydrophobizing agent, based on the hydrophilic thermal-insulation
molding, is from 0.5 to 10% by weight.
12. The process according to claim 1, which is carried out
continuously.
13. The process according to claim 2, wherein in the heating, a
reaction temperature T.sub.reaction is from 50.degree. C. to
500.degree. C.
14. The process according to claim 2, wherein a contact time during
the contacting and a heating time during the heating are in each
case from 1 minute to 1 hour.
15. The process according to claim 3, wherein a contact time during
the contacting and a heating time during the heating are in each
case from 1 minute to 1 hour.
16. The process according to claim 2, wherein the contacting and
the heating takes place in a chamber, and wherein the
hydrophobizing agent is introduced into the chamber until a
pressure difference .DELTA.p is .gtoreq.20 mbar, wherein
.DELTA.p=p.sub.2-p.sub.1, and p.sub.1=pressure in the chamber
before the introduction of the hydrophobizing agent,
p.sub.2=pressure in the chamber at which the introduction of the
hydrophobizing agent is stopped.
17. The process according to claim 3, wherein the contacting and
the heating takes place in a chamber, and wherein the
hydrophobizing agent is introduced into the chamber until a
pressure difference .DELTA.p is .gtoreq.20 mbar, wherein
.DELTA.p=p.sub.2-p.sub.1, and p.sub.1=pressure in the chamber
before the introduction of the hydrophobizing agent,
p.sub.2=pressure in the chamber at which the introduction of the
hydrophobizing agent is stopped.
18. The process according to claim 13, wherein the contacting and
the heating takes place in a chamber, and wherein the
hydrophobizing agent is introduced into the chamber until a
pressure difference .DELTA.p is .gtoreq.20 mbar, wherein
.DELTA.p=p.sub.2-p.sub.1, and p.sub.1=pressure in the chamber
before the introduction of the hydrophobizing agent,
p.sub.2=pressure in the chamber at which the introduction of the
hydrophobizing agent is stopped.
19. The process according to claim 2, wherein the fine-particle
silica is a fumed silica.
20. The process according to claim 3, wherein the fine-particle
silica is a fumed silica.
Description
The invention relates to a process for the production of a
hydrophobic thermal-insulation moulding comprising silica.
The person skilled in the art is aware that hydrophobic silicas are
not adequately amenable to compaction and do not give satisfactory
results in press processes. A mixture comprising hydrophobic silica
likewise does not give satisfactory results in press processes.
EP-A-1988228 therefore proposes adding organosilanes during the
mixing procedure for a thermal-insulation mixture based on fumed
silica, opacifier and fibre materials. An important factor here for
achieving full hydrophobization is vigorous, homogeneous mixing of
the components. Immediately after the addition, this mixture is
deformable and can be used successfully in a press process. The
reaction of the organosilanes with the silanol groups of the silica
here takes place during the press procedure or immediately
thereafter.
WO2011/069923 discloses use of low-volatility organosilanes or
organosiloxanes for the hydrophobization of a thermal-insulation
mixture comprising fumed silica. These adsorb onto the pulverulent
individual constituents of the thermal-insulation mixture, without
any subsequent chemical reaction during or after a press
procedure.
WO2011/150987 finally uses solid hydrophobizing agents with
softening point from -30.degree. C. to 600.degree. C. for the
production of thermal-insulation sheets.
It has been found that in the processes mentioned where the
hydrophobizing agent is added before the press procedure it is
difficult to obtain stable mouldings, in particular when the
hydrophobization produces gaseous products.
WO2013/013714 therefore also proposes that the hydrophobization be
carried out after the press procedure. At least one organosilane in
the form of vapour is used here, at subatmospheric or
superatmospheric pressure, to treat the hydrophilic moulding
present in a chamber after the press procedure.
Both of the processes mentioned in the prior art that lead to
hydrophobic thermal-insulation mouldings have disadvantages, said
processes being the addition of the hydrophobizing agent to the
pulverulent thermal-insulation mixture before the press process and
hydrophobization after the press process to give thermal-insulation
mouldings.
The processes where the hydrophobizing agent is added before the
press process have the disadvantage that the density of the silicas
increases in a manner that is difficult to control during the press
process and leads to inhomogeneity of material distribution, and
also to variations in mechanical stability of the mouldings.
The processes where hydrophobization takes place after the press
process have the disadvantage that an additional step is necessary
and that penetration of the pressed material is non-uniform and
incomplete. When processes operate at superatmospheric pressure,
adverse effects on the material are in particular observed.
The technical object of the present invention therefore consisted
in providing a process which can produce a hydrophobic
thermal-insulation moulding and which minimizes said
disadvantages.
It would moreover be desirable that said process could be carried
out continuously. WO 20051028195 provides the continuous production
of hydrophilic thermal-insulation sheets by using a belt press.
However, in that context it has not been found possible to achieve
continuous hydrophobization of said thermal-insulation sheets.
Another technical object of the present invention was therefore to
provide a process which permits continuous production of
hydrophobic thermal-insulation sheets.
The invention provides a process for the production of a
hydrophobic thermal-insulation moulding, in particular of a
thermal-insulation sheet, where a hydrophilic thermal-insulation
moulding composed of a thermal-insulation mixture comprising a
fine-particle silica, IR opacifier and fibre material is brought
into contact with a hydrophobizing agent in vapour form with
formation of a thermal-insulation moulding coated with
hydrophobizing agent,
and this is then subjected to a press process and during the press
process and/or after the press process is reacted with the
hydrophobizing agent with formation of the hydrophobic
thermal-insulation moulding,
where
a) the density of the hydrophobic thermal-insulation moulding after
the press process and after the reaction with the hydrophobizing
agent is from 100 to 250 kg/m.sup.3, preferably from 130 to 200
kg/m.sup.3, and
b) the density of the hydrophilic thermal-insulation moulding on
contact with the hydrophobizing agent is from 50% to less than
100%, preferably from 50 to 99%, particularly preferably from 60 to
95%, very particularly preferably from 70 to 90%, of the density of
the hydrophobic thermal-insulation moulding.
Essential feature of the invention is contact between a
hydrophobizing agent in the form of vapour and a hydrophilic
thermal-insulation moulding. In contrast to the prior art, in which
the hydrophobizing agent is added to a pulverulent
thermal-insulation mixture before the press process, the process of
the invention permits production of a thermal-insulation moulding
that is uniformly and entirely hydrophobic.
The expression "hydrophobic thermal-insulation moulding" means that
when water-methanol wettability of same is determined sedimentation
is observed at 15% by volume of methanol or more, preferably at 20%
by volume of methanol or more, particularly preferably at 25% by
volume of methanol or more, in particular at from 25 to 50% by
volume of methanol.
Water-methanol wettability is determined by weighing portions from
different regions of the hydrophobic thermal-insulation moulding,
in each case 0.2 g.+-.0.005 g, into transparent centrifuge tubes.
8.0 ml of a methanol/water mixture using respectively 10, 20, 30,
40, 50, 60, 70 and 80% by volume of methanol are added to each
weighed quantity. The sealed tubes are shaken for 30 seconds and
then centrifuged for 5 minutes at 2500 min.sup.-1. The sediment
volumes are read off, converted to percentages, and plotted on a
graph against methanol content (% by volume). The water-methanol
wettability value described here corresponds to the inflection
point of this curve. The higher the methanol content value (% by
volume), the greater the hydrophobicity.
Accordingly, a thermal-insulation moulding exhibiting sedimentation
at methanol content of 15% by volume or more is regarded as
hydrophobic. The hydrophilic thermal-insulation moulding is
obtained via compaction of the thermal-insulation mixture.
A hydrophilic thermal-insulation moulding is converted to a
hydrophobic thermal-insulation moulding via reaction of the
superficial hydroxy groups of at least one of its constituents with
a hydrophobizing agent.
According to the invention, hydrophilic and hydrophobic
thermal-insulation mouldings are structures that are intrinsically
stable and can be handled, whereas the thermal-insulation mixture
is composed of pulverulent constituents and fibres. The
distribution of the constituents of the thermal-insulation mixture
is very substantially homogeneous in the hydrophilic, and also
hydrophobic, thermal-insulation moulding.
It is preferable that thermal-insulation mixture and
thermal-insulation moulding comprise only subordinate quantities of
binder, or are entirely free therefrom. The expression
"subordinate" means that these proportions make no significant
contribution to the stability of the thermal-insulation
moulding.
According to the invention, the hydrophilic thermal-insulation
moulding is brought into contact with a hydrophobizing agent. The
contact temperature T.sub.contact here is selected in such a way
that no, or only a subordinate extent of, hydrophobization reaction
takes place. T.sub.contact is generally below or equal to 80% of
the reaction temperature of the respective hydrophobizing agent. It
is preferable that T.sub.contact is from -30 to 150.degree. C.,
particularly from 20 to 100.degree. C.
During the subsequent press process and/or thereafter the
hydrophobizing agent will react with reactive groups on the surface
of the components of the thermal-insulation mixture to form the
hydrophobic thermal-insulation moulding. The temperature
T.sub.reaction depends inter alia on the nature of the
hydrophobizing agent. It is preferable that T.sub.reaction is from
50 to 500.degree. C., particularly from 100 to 300.degree. C.
It is preferable that the contact time and the reaction time are in
each case from 1 minute to 1 hour, particularly from 5 to 10
minutes.
The process of the invention is preferably implemented in a manner
where the contact and the reaction of the hydrophobizing agent with
the hydrophilic thermal-insulation moulding takes place in a
chamber, and the hydrophobizing agent here is introduced into the
chamber until the pressure difference .DELTA.p is .gtoreq.20 mbar,
where .DELTA.p=p.sub.2-p.sub.1, and p.sub.1=pressure in the chamber
before introduction of the hydrophobizing agent, p.sub.2=pressure
in the chamber at which the introduction of the hydrophobizing
agent is stopped. The process of the invention is preferably
implemented in a manner such that 200 mbar.ltoreq..DELTA.p.ltoreq.5
bar, particularly 500 mbar.ltoreq..DELTA.p.ltoreq.2000 mbar, very
particularly 500 mbar.ltoreq..DELTA.p.ltoreq.1000 mbar.
In one particular embodiment of the invention, the process is
implemented in a manner such that pressure in the chamber before
introduction of the hydrophobizing agent is smaller than
atmospheric pressure. In a particularly advantageous embodiment,
0.1 mbar.ltoreq.p1.ltoreq.atmospheric pressure. Particular
preference is given to a variant where 1 mbar.ltoreq.p1.ltoreq.500
mbar. In this particular embodiment, the hydrophobizing agent is
therefore introduced into an evacuated chamber. In this
subatmospheric-pressure process the hydrophobizing agent is
"sucked" into even the finest pores of the hydrophilic
thermal-insulation moulding, and achieves ideal distribution.
In another particular embodiment of the invention, the process is
implemented in a manner such that pressure in the chamber before
introduction of the hydrophobizing agent is atmospheric pressure or
above. In an advantageous embodiment here, atmospheric
pressure.ltoreq.p1.ltoreq.10 bar. In this superatmospheric-pressure
process the hydrophobizing agent is "forced" into the pores of the
hydrophilic thermal-insulation moulding, and thus achieves ideal
distribution.
According to the invention, fine-particle silicas are used. These
have a specific structure. Primary particles of size from 5 to 50
nm accrete to give larger aggregates which in turn combine to give
even larger structures, the agglomerates.
Fumed silicas can preferably be used. They are produced via flame
hydrolysis of volatile silicon compounds such as organic and
inorganic chlorosilanes. This process uses a flame formed via
combustion of hydrogen and of an oxygen-containing gas for the
reaction of a hydrolysable silicon halide in the form of vapour or
in gaseous form. The combustion flame here provides water for the
hydrolysis of the silicon halide, and sufficient heat for the
hydrolysis reaction. Silica produced in this way is termed fumed
silica. This process initially forms primary particles which are
almost free from interior pores. These primary particles then fuse
during the process by way of what are known as "sinter necks" to
give aggregates. By virtue of this structure, fumed silica is an
ideal thermal-insulation material, since the aggregate structure
provides adequate mechanical stability, minimizes heat transfer due
to conductivity in the solid by way of the "sinter necks", and
produces sufficiently high porosity. The BET surface area of the
fumed silica can be from 50 to 1000 m.sup.2/g. Fumed silicas with
BET surface area of from 150 to 600 m.sup.2/g are particularly
preferred, and those with from 200 to 400 m.sup.2/g are very
particularly preferred.
The process of the invention can equally use precipitated silicas.
These are obtained via reaction of an alkali water glass with
sulphuric acid. The precipitate is filtered, washed and dried. The
BET surface area of the precipitated silica can be from 20 to 2000
m.sup.2/g. Precipitated silicas have proved to be less effective
than fumed silicas in their use as thermal-insulation mouldings.
However, the precipitated silica disclosed in WO2010/091921, with
modified tamped density 70 g/l or less, provides an alternative to
fumed silicas.
The proportion of the fine-particle silica is preferably from 70 to
95% by weight, based on the thermal-insulation mixture.
The opacifier is preferably selected from the group consisting of
titanium oxide, zirconium oxide, ilmenite, iron titanate, iron
oxide, zirconium silicate, silicon carbide, manganese oxide and
carbon black. It is preferable that these opacifiers have a maximum
at from 1.5 to 10 .mu.m in the infrared region of the spectrum. The
size of these particles is preferably from 0.5 to 15 .mu.m. The
proportion thereof in the thermal-insulation mixture is preferably
from 2 to 20% by weight.
Fibres are used for mechanical reinforcement. These fibres can
derive from an inorganic or organic source. Examples of inorganic
fibres that can be used are glass wool, rock wool, basalt fibres,
slag wool and ceramic fibres, these deriving from melts comprising
aluminium and/or silicon dioxide, and also from other inorganic
metal oxides. Examples of pure silicon dioxide fibres are silica
fibres. Examples of organic fibres which can be used are cellulose
fibres, textile fibres and synthetic fibres. The diameter of the
fibres is preferably from 1 to 12 .mu.m, particularly preferably
from 6 to 9 .mu.m, and the length is preferably from 1 to 25 mm,
particularly preferably from 3 to 10 mm.
The proportion of the fibre material is preferably from 3 to 10% by
weight, based on the thermal-insulation mixture.
The thermal-insulation mixture can moreover comprise inorganic
filler materials. Materials that can be used are arc silicas,
SiO.sub.2-containing fly ash produced via oxidation reactions of
volatile silicon monoxide during electrochemical production of
silicon or ferrosilicon. It is moreover possible to use naturally
occurring SiO.sub.2-containing compounds such as diatomaceous
earths and kieselguhrs. It is likewise possible to add thermally
expanded minerals such as perlites and vermiculites, and
fine-particle metal oxides such as aluminium oxide, titanium
dioxide, iron oxide. The proportion of the inorganic filler
materials is preferably not more than 10% by weight, based on the
thermal-insulation mixture. In one particularly preferred
embodiment, the thermal-insulation mixture is very substantially
free from these inorganic additives.
Materials that can be used as hydrophobizing agent are especially
organosilanes. Selection of these is not subject to any
restriction, but a factor requiring consideration is that the
hydrophobizing agent according to the invention is used in the form
of vapour. One or more organosilanes from the group consisting of
R.sub.n--Si--X.sub.4-n, R.sub.3Si--Y--SiR.sub.3,
R.sub.nSi.sub.nO.sub.n,
(CH.sub.3).sub.3--Si--(O--Si(CH.sub.3).sub.2).sub.n--OH,
HO--Si(CH.sub.3).sub.2--(O--Si(CH.sub.3).sub.2).sub.n--OH, where
n=from 1 to 8; R.dbd.--H, --CH.sub.3, --C.sub.2H.sub.5; X.dbd.--Cl,
--Br; --OCH.sub.3, --OC.sub.2H.sub.6, --OC.sub.3H.sub.8, Y.dbd.NH,
O, can preferably be used. Explicit mention may be made of the
following: (CH.sub.3).sub.3SiCl, (CH.sub.3).sub.2SiCl.sub.2,
CH.sub.3SiCl.sub.3, (CH.sub.3).sub.3SiOC.sub.2H.sub.6,
(CH.sub.3).sub.2Si(OC.sub.2H.sub.6).sub.2,
CH.sub.3Si(OC.sub.2H.sub.6).sub.3,
(CH.sub.3).sub.3SiNHSi(CH.sub.3).sub.3,
(CH.sub.3).sub.3SiOSi(CH.sub.3).sub.3, the cyclic siloxanes
(CH.sub.3).sub.8Si.sub.4O.sub.4 and
(CH.sub.3).sub.6Si.sub.3O.sub.3, and the low-molecular-weight
polysiloxanol (CH.sub.3).sub.3Si(OSi(CH.sub.3).sub.2).sub.4OH.
Particular preference is given to (CH.sub.3).sub.3SiCl,
(CH.sub.3).sub.2SiCl.sub.2, CH.sub.3SiCl.sub.3,
(CH.sub.3).sub.3SiNHSi(CH.sub.3).sub.3 and
(CH.sub.3).sub.8Si.sub.4O.sub.4. The proportion of the
hydrophobizing agent is preferably from 0.5 to 10% by weight,
preferably from 1 to 7% by weight, based on the hydrophilic
thermal-insulation moulding.
One particular embodiment of the invention provides that the
process is carried out continuously, where the hydrophobic
thermal-insulation moulding is a hydrophobic thermal-insulation
sheet, preferably of thickness from 1 to 20 cm, and where the
contact, the press process and the hydrophobizing reaction take
place between two gas-permeable, moving belts of a press.
The provision of the hydrophilic thermal-insulation sheet via
subjection of the thermal-insulation mixture to a press process can
be achieved here as disclosed in WO2005/028195. The
thermal-insulation mixture here is applied to a gas-permeable
belt.
It is preferable that the contact between the resultant hydrophilic
thermal-insulation sheet and the hydrophobizing agent, and the
reaction of the hydrophobizing agent, is achieved in a chamber
surrounding the belt. It is thus possible to use subatmospheric or
superatmospheric pressure to pass the hydrophobizing agent through
the hydrophilic thermal-insulation sheet. The hydrophilic
thermal-insulation sheet with its coating of hydrophobizing agent
is then subjected to a press process to give the final density, and
during this and/or after the press process is reacted at elevated
temperature.
The gas-permeable belt is composed by way of example of a solid
belt, preferably of steel, without perforations, on which there is
at least one woven mesh with pore diameter from 100 .mu.m to 30 mm,
on which there is at least one nonwoven or woven fabric with pore
diameter from 10 .mu.m to 450 .mu.m. The construction of the second
belt is a mirror reflection of the first belt. This design permits
removal of air released when the thermal-insulation mixture is
subjected to the press process, and also of gaseous reaction
products formed during the hydrophobizing reaction, for example
hydrogen chloride or ammonia.
EXAMPLES
The thermal-insulation mixture used is composed of 77.7% by weight
of AEROSIL.RTM.300, Evonik Industries, 19.4% by weight of 900 F
silicon carbide from Keyvest and 2.9% by weight of BELCOTEX 225 SC6
glass fibres from Belchem. The thermal-insulation mixture is
subjected to a press process to give sheets measuring
140.times.90.times.20 mm in a press composed of female press mould,
sinter plate and coat. The desired final density of the
thermal-insulation sheets is 165 kg/m.sup.3.
Example 1 (Comparative Example)
The final density of the sheet produced from the thermal-insulation
mixture by means of the press is 165 kg/m.sup.3. Press and sheet
are then heated to 165.degree. C. During this procedure, 20 g of
hexamethyldisilazane (HMDS) are vaporized. The female press mould
is evacuated to a subatmospheric pressure of 6 mbar, and the
vaporized HMDS is sucked through the sheet. After 10 min a sheet
can be removed after depressurization. Determination of
water-methanol wettability of various samples of this sheet reveals
adequately good hydrophobization.
Example 2
The density of the sheet produced from the thermal-insulation
mixture by means of the press is 130 kg/m.sup.3, corresponding to
80% of the final density. The temperature of press and sheet is
about 20.degree. C. 20 g of HMDS are vaporized. The female press
mould is evacuated to a subatmospheric pressure of 6 mbar, and the
vaporized HMDS is sucked through the sheet. After 10 min the
material is compacted to the final density of 165 kg/m.sup.3, and
then the sheet is heated to 165.degree. C. After 10 min a
hydrophobic sheet can be removed. Determination of water-methanol
wettability of various samples of this sheet reveals uniform
hydrophobization of the entire product. Water-methanol wettability
is about 30% by volume of methanol.
Example 3
The density of the sheet produced from the thermal-insulation
mixture by means of the press is 100 kg/m.sup.3, corresponding to
60% of the final density. The temperature of press and sheet is
about 80.degree. C. 20 g of HMDS are vaporized. The female press
mould is evacuated to a subatmospheric pressure of 6 mbar, and the
vaporized HMDS is sucked through the sheet. After 10 min the
material is compacted to the final density of 165 kg/m.sup.3, and
then the sheet is heated to 165.degree. C. Determination of
water-methanol wettability of various samples of this sheet reveals
uniform hydrophobization of the entire product.
Water-methanol wettability is about 30% by volume of methanol.
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